| 摘要 |
A dual filtering system, especially for swimming pools, in which dirt and any large particulates are removed by passing a liquid feed through said filter bed and minute impurities are then removed by passing the liquid filtrate through a multiplicity of vertically aligned, diatomaceous earth filter grid units. This permits the diatomaceous earth filter grid units to be operated for a protracted period of time with little, if any, need to backwash them. The filter grid units and the sand filter bed are disposed within a single tank in separate zones, one located above the other in a spaced, coaxial arrangement. The pressure differential between the two zones is automatically regulated during filtration by a check valve means. Each of the filter grid units is removably connected to radial arms of a manifold assembly and spaced apart from another. The grids are comprised of a rigid, sock-like pervious filter tube tightly fitted over a rigid, perforated tubular frame. This arrangement prevents adjacent grid units from tangling and losing effectiveness and also permits quick, easy removal and/or replacement of individual filter grid units.
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